我想看看 postgres 中 DO 块内的循环迭代需要多长时间。基本布局如下：
DO $$
declare v_time timestamptz;
declare i record;
begin
for i in select generate_series(1, 5) t
loop
select current_timestamp into v_time;
perform pg_sleep(i.t);
-- something done here (pg_sleep to ensure some time passes)
raise notice '%', v_time - (select current_timestamp);
-- expect negative interval from RAISE.
end loop;
end; $$;
但是，当我运行此命令时（已在 Postgres 13 和 9 上尝试过），我得到返回 0S 的间隔：
NOTICE: 00:00:00
NOTICE: 00:00:00
NOTICE: 00:00:00
NOTICE: 00:00:00
NOTICE: 00:00:00
DO
Query returned successfully in 15 secs …